The Birth, Life, and Death of Stars Stellar Evolution The Birth, Life, and Death of Stars

The Universe Everything The Universe is 13.72 billion years old All matter, space, and time The Universe is 13.72 billion years old

Cosmology The study of the origin of the Universe

An average sized Star About 4.5 billion years old The Sun

What is a Solar System? A star and everything that revolves around it Our Solar System is about ___ years old

A light-year A unit of distance, not time The distance light travels in one year 6 Trillion miles

Distance to Sun 93 million miles 8.3 light-minutes

Proxima Centauri The closest star to our sun About 4 light-years away

Galaxies Stars are not evenly distributed in space. They are in groups called Galaxies.

Types and Sizes of Galaxies Types: Elliptical, Spiral, Irregular Two sizes Giant Dwarf

The Milky Way Galaxy 100,000 light years across Has Hundreds of billions of stars

Galaxy Clusters A Group of Galaxies Local Group 2 mly across 3 large & about 2 dozen dwarf Andromeda 2.2 mly

Galaxy Superclusters A cluster of clusters The Local (Virgo) Supercluster 100 clusters 100 mly across

Nearest Superclusters

Galaxy Superclusters

The Visible Universe

How big is the Universe? The visible universe is 28 billion light years in diameter. Why is that all that is visible? The entire universe may be much bigger

How many Galaxies are there? Hundreds of billions Each has hundreds of billions of stars

Edwin Hubble 1920’s Discovered other galaxies Discovered the Universe is expanding

The Expanding Universe The Red Shift Doppler effect

The Doppler Effect

The Big Bang Tremendous explosion started the expansion of the universe All of the matter and energy of the universe was contained at one point

Characteristics of Stars

Star Properties and Classification Color Temperature Age Apparent brightness Distance from Earth

Star Brightness Apparent Magnitude Absolute Magnitude How bright it looks from Earth Absolute Magnitude How much light it actually produces

Apparent Magnitude (Brightness) Depends on actual brightness (luminosity) and distance away

Hertzsprung-Russell (H-R) Diagram Compares a star’s Temperature (color) and its … Absolute Magnitude (Brightness)

Hertzsprung-Russell (H-R) Diagram

Hertzsprung-Russell (H-R) Diagram Things to Know Color depends on temperature Blue, White, Yellow, Orange, Red The higher the Temperature the Brighter the Star (if in the main sequence) White Dwarfs and Red Giants are exceptions The Sun is in the main sequence (90% of stars)

Star Relative Size The Sun is an averaged sized star

The Formation and Life Cycle of Stars Stellar Evolution The Formation and Life Cycle of Stars

Star Formation Originate in gas clouds in space called Nebula Mostly Hydrogen Gravity pulls it together

Nebula The contraction heats the gases When it gets hot enough (27 million degrees) nuclear fusion starts

Nuclear Fusion Hydrogen nuclei are fused to make helium The reaction produces heat energy, which causes more fusion

How big is a Nebula? The Orion Nebula is about 2.5 light years across

Old Age When the hydrogen runs low Contractions make more heat Causes nuclear fusion to make heavier elements Expansion results in a Red Giant

White Dwarf When energy is used, it shrinks to make a white dwarf

Supernovas Collapses abruptly then explodes Billions of times brighter Creates heavier elements Occurs only in very massive stars

After a Supernova The outer layers are blasted into space to create a new nebula (starts the cycle over) The core collapses to form a neutron star

Neutron Star Left over after a supernova 1 teaspoon weighs billions of tons

Black Holes A star so dense, even light can not escape

Formation of Heavier Elements Elements heavier than hydrogen are formed by nuclear fusion in Stars Elements heavier then iron form during a Supernova

The End